Soil mineral N and soil water content at planting, biomass accumulation, yield and grain quality parameters (hectolitermass and protein percentage) were measured on an unfertilized and recommended-N-application treatment during two consecutive growing seasons (1997-1998). The trials were planted in a fallow-wheat-wheat cropping system at three representative localities in the summer rainfall region of South Africa. High levels of available soil water and mineral N were measured following the fallow period preceding the start of the trials in 1997. For example, soil water content was 81.7%, 69.6%, and 78.2% of DUL at Bethlehem, Kroonstad and Petrusburg respectively. Although comparable total soil profile water contents to 1997 were measured in 1998 at all three sites, the cultivation zone (0-400 mm) had a substantially lower soil water content. This was due to erratic rainfall distribution during the fallow period, which prevented effective soil cultivation management, subsequent soil water conservation and residue decomposition. Undecomposed residue in the cultivation layer at planting appeared to affect availability of soil mineral N to the growing crop. At planting in 1998, undecomposed crop residue amounted to 53.6% at Bethlehem, 32.5% at Kroonstad and 46.9% at Petrusburg of that added at harvest in 1997. Soil mineral N was lower at planting in 1998 compared to 1997 due to decomposing residue (C:N ratio of above 73) in the cultivation zone immobilizing soil mineral N. This reduced initial growth, N accumulation, yield, and grain protein percentage without additional fertilizer N. Distribution of soil mineral N showed notable amounts in the 600-1200 mm soil layers, with limited changes over the trial period. This was linked to low root exploration of these soil layers (10-15% of total root distribution). The ratios of soil mineral NH(4+):N0(3)- for the different soil layers indicated similar values over the trial period. Climatic data for the localities indicated differences in the amount and distribution of rainfall and temperatures during the study period, which influenced crop development, yield and grain protein percentage. At Bethlehem above average in-season rainfall was measured during 1997, at Kroonstad average rainfall and at Petrusburg below average in-season rainfall. Response to applied N at the localities varied in magnitude during 1997. Nitrogen application significantly increased N concentrations of plant components, N uptake, yield and grain protein percentage, although values for all these parameters were lower in 1998 than in 1997. Indeed higher yields were produced in 1997 (mean=1.838 t ha(-1)) compared to 1998 (mean=0.980 t ha(-1)). A significant yield response to applied N was measured at the two higher yielding localities in both cropping years, but there was no significant response at the lower yielding locality. The limiting factors appeared to be the availability of soil water and residual soil mineral N. From the calculated response functions, the variables soil water content at planting, soil mineral N content at planting, in-season rainfall, and added fertilizer N explained the bulk of the variations in grain protein percentage, plant N uptake, and yields. It was concluded that the present fertilizer N recommendation system for dryland wheat production, which is based on fertilizer response curves for specific yield potentials, should be augmented by using initial soil mineral N and water contents in the profile measured prior to planting. / Thesis (M.Sc.Agric.)-University of Natal, Pietermaritzburg, 2002.

Flooding cycle in wetland rice (Oryza sativa L.) production systems is often subject to seasonal and cultural variations which may affect the availability and uptake of nitrogen in different ways. These factors may more or less influence the physiological and growth responses of the plant. In an effort to improve productivity in rice cropping systems, two controlled environment studies and a field trial were conducted to evaluate the growth and yield responses of rice to different flooding regimes and nitrogen fertilizer management strategies. In the first glasshouse trial, an upland cultivar (GM-1) was used to study the effects of four flooding regimes and three nitrogen application rates on the tillering, yield components and grain yield of rice. The field study determined the applicability of the results of the glasshouse trial to out-door environmental conditions, with the aim of gaining further insight into the impact of nitrogen application strategy on tiller and grain qualities. Two wetland cultivars (FKR-19 and N-19) and GM-1 were used to evaluate the effects of two flooding regimes and two nitrogen topdressing patterns. The second glasshouse trial determined the effect of hydro-priming on the establishment of direct seeded rice, and the effect of flooding on aerenchyma formation in rice roots. Results of the studies showed that flooding with standing water of 5 cm above the soil surface, irrespective of when it occurred, and nitrogen application increased the number of tillers and panicles, above ground dry matter, nitrogen uptake and grain yield of rice. However, late flooding and high nitrogen application rate of 220 kg ha-1 were found to encourage the production of late tillers, thereby reducing the efficiency of nitrogen use for grain production. Nitrogen application in three split doses tended to increase plant nitrogen content at heading; it slightly increased the protein content of the grains at maturity, but reduced the amylose content of the starch granules. Nitrogen application in two split doses led to increased grain yield in non-flooded plants, while the three-split treatment increased nitrogen uptake and grain yield in the flooded plants. Flooding significantly increased aerenchyma formation in the cortical tissues of rice roots, particularly at 50 mm behind the root tips. Hydro-priming seeds for 48 h improved plant establishment by shortening the germination and emergence times, and increasing the height and dry matter accumulation of seedlings, thereby ameliorating the susceptibility of rice to flooding stress. Overall, the thesis affirmed that controlled flooding is beneficial to rice production since it enhanced the growth and yield of the plant. It further revealed that early flooding and appropriate timing of moderate nitrogen application can ensure the conservation of water and nitrogen resources, including the quality of the environment, with no significant consequence for yield and productivity of the crop. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2010.

Copy of author's previously published work inserted. / Bibliography: leaves 147-189. / xxi, 189 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This project examines the uptake of mineral N from the subsoil after anthesis and its effect on grain protein concentration (GPC) of wheat. The overall objective is to examine the importance of subsoil mineral N and to investigate the ability of wheat to take up N from the subsoil late in the season under different conditions of N supply and soil water availability. Greenhouse experiments investigate the importance of subsoil mineral N availability on GPC of wheat and the factors that contribute to the effective utilisation of N. The recovery of N from subsoil, the effect of split N application on GPC and short term N uptake by the wheat at different rooting densities are also studied. / Thesis (Ph.D.)--University of Adelaide, Dept. of Soil Science, 1997

CNPq; Fundação Araucária / A região do Sudoeste do Paraná apresenta o setor agrário bem desenvolvido, com ênfase na produção leiteira de pela agricultura familiar. A base nutricional dessas propriedades são as pastagens formadas por gramíneas tropicais, as quais apresentam uma diminuição em sua produção de fitomassa em determinada época do ano, com a queda na intensidade luminosa e temperatura. A implantação de pastagens temperadas, principalmente de aveia, é uma estratégia comum na região para a atividade. Avaliou-se os efeitos dos níveis de nitrogênio no crescimento, desenvolvimento, acúmulo de fitomassa, composição química, cinética ruminal e produção de gases de efeito estufa. O trabalho foi conduzido na UTFPR-DV nos anos de 2013 e 2014, em blocos ao acaso com quatro níveis de adubação N (0,60, 120 e 240 KgN.ha-1) com 3 repetições, em períodos de corte a cada 21 dias, usando-se cultivares de aveia branca (Avena sativa L.) URS Guapa e IPR126. Foram analisados taxa de assimilação de CO2, concentração intracelular de CO2, taxa de transpiração, temperatura da folha, teor de clorofila, produção de fitomassa, proteína, FDN, lignina, EE, produção de gás em relação aos teores de carboidratos de rápida degradação e de degradação lenta, bem como CH4, CO2 e N2O.Para IPR 126 no ano de 2013 houve efeito significativo nas variáveis PB, CT, k1, eficiência do uso da água, transpiração e temperatura foliar, enquanto que para o ano de 2014, as variáveis foram CT, vf1, k1, vf2, número de perfilhos e eficiência do uso da água. Para a cultivar URS Guapa, no ano de 2013, houve efeito significativo para as variáveis peso das folhas (em gramas) e temperatura foliar, enquanto que no ano de 2014, número de perfilhos, transpiração e temperatura foliar foram significativos.Observou-se que a cultivar IPR 126 foi mais influenciada pelos níveis de adubação que a cultivar URS Guapa, em todos os anos e os gases de efeito estufa não foram afetados. / The Southwest region of Paraná presents the well-developed agrarian sector, with emphasis on dairy production from family farming. The nutritional base of these properties are pastures formed by tropical grasses, which present a decrease in their phytomass production at a given time of year, with the decrease in luminous intensity and temperature. The implementation of temperate pastures, mainly of oats, is a common strategy in the region for the activity. The effects of nitrogen levels on growth, development, phytomass accumulation, chemical composition, ruminal kinetics and greenhouse gas production were evaluated. The work was conducted in UTFPR-DV in the years of 2013 and 2014, in randomized blocks with four levels of N fertilization (0.60, 120 and 240 KgN.ha-1) with 3 replications, in cut-off times every 21 Days, using white oats (Avena sativa L.) URS Guapa and IPR126. Were analysed CO2 assimilation rates, intracellular CO 2 concentration, transpiration rate, leaf temperature, chlorophyll content, phytomass production, protein, NDF, lignin, EE, gas production in relation to fast-degraded carbohydrate. In the year of 2013, there was a significant effect on the variables PB, CT, k1, water use efficiency, transpiration and foliar temperature, while for the year 2014, Variables were CT, vf1, k1, vf2, number of tillers and water use efficiency. For the cultivar URS Guapa, in the year 2013, there was a significant effect for the variables leaf weight (in grams) and leaf tempreture, while in the year 2014, number of tillers, transpiration and leaf temperartura were significant. It was observed that The cultivar IPR 126 was more influenced by levels of fertilization than the cultivar URS Guapa, in all years and greenhouse gases were not affected.

A integração lavoura-pecuária além de intensificar o uso da terra, acrescentando renda ao produtor rural, traz muitos outros benéficos aos sistemas agrícolas. Um deles é a maior eficiência no uso dos fertilizantes nitrogenados, ocasionado pela maior ciclagem e reciclagem de nutrientes entre a fase pastagem e a fase lavoura, o que diminuí custos de produção e torna o sistema mais sustentável a longo prazo, devido a menor taxa de perdas de N. Neste contexto, o objetivo deste trabalho foi avaliar as perdas por volatilização de amônia em função da aplicação de N e da altura de manejo de pasto em área de integração lavoura-pecuária. O experimento foi realizado em uma área de 14 ha, onde desde 2012 vem sendo conduzido um experimento em longo prazo com ILP sob Plantio Direto. Foram avaliados quatro cultivos em rotação durante duas safras agrícolas, sendo eles: azevém-feijão (2016/2017), e aveia-milho (2017/2018). O delineamento experimental para a cultura de inverno foi em blocos ao acaso em esquema fatorial (2x2x7), com três repetições. O primeiro fator foi tempo de aplicação de nitrogênio (N) no sistema: N aplicado na pastagem (N-Pastagem) e sendo estas as únicas parcelas a receberem N de cobertura na dose 200 kg de N ha-1 em uma única aplicação nesta fase experimental as quais foram comparadas com as parcelas denominadas N-Adubação Grãos, as quais não receberam adubação nitrogenada na fase de pastejo. O segundo fator foi altura de pasto, Alta Altura (AA) e Baixa Altura (BA), 25 e 10 cm (alturas pretendidas), respectivamente. Como terceiro fator foram avaliados os dias de coleta após a aplicação de N, sendo estas realizadas no 2°, 4°, 6°, 8°, 10°, 12° e 14° dia após a aplicação de ureia. Para a cultura de grãos foram adicionados mais um fator (2x2x7x4), sendo as doses crescentes de N: 0; 50; 100 e 150 kg ha-1, e 0; 100; 200 e 300 kg ha-1, para a cultura do feijão e milho, respectivamente. As mesmas foram alocadas em subparcelas dentro de cada parcela, no momento da aplicação do N em cobertura no tratamento N-Adubação Grãos. A avaliação de volatilização de amônia foi realizada pelo método de coletores semiabertos estáticos e a quantificação do teor de amônia foi realizada pelo método de colorimetria. As perdas por volatilização de amônia, tanto para as culturas de inverno como para as culturas de verão foram influenciadas pelos tratamentos a qual forma submetidos, e foram altamente dependentes das condições climáticas no momento da aplicação de N. As perdas acumuladas por volatilização de amônia provocadas pela adubação nitrogenada (ureia) foram mínimas, sendo inferiores a 1,5 % nos dois anos de avaliação na fase de pastejo. Na fase de cultivo de feijão e milho a perda máxima de volatilização amônia acumulada observada foi de 5,37% e 4,0 %, respectivamente. Uma maior pressão de pastejo resultou em menores perdas por volatilização de amônia durante a fase de pastejo e contrariamente, durante a fase de cultivo de grãos uma maior pressão de pastejo, aplicada na pastagem cultivada anteriormente, resultou em maiores perdas por volatilização da amônia. / The crop-livestock integration, besides intensifying the use of land, adding income to the rural producer, brings many other benefits to the agricultural systems. One of them is the greater efficiency in the use of nitrogen fertilizers, caused by the greater cycling and recycling of nutrients between the pasture phase and the cropping phase, which reduces production costs and makes the system more sustainable in the long term, due to the lower rate of losses of N. In this context, the objective of this work was to evaluate the losses by volatilization of ammonia due to the application of N and the height of pasture management in the area of crop-livestock integration. The experiment was carried out in an area of 14 ha, where since 2012 a long-term experiment has been conducted with ILP under Plantio Direto. Four rotating crops were evaluated during two agricultural crops: ryegrass (2016/2017), and oat-corn (2017/2018). The experimental design for the winter crop was in randomized blocks in a factorial scheme (2x2x7), with three replications. The first factor was nitrogen (N) application time in the system: N applied to the pasture (N-Pasture) and these were the only plots to receive coverage N at the dose 200 kg of N ha-1 in a single application at this stage which were compared with the plots denominated N- Fertilization Grains, which did not receive nitrogen fertilization in the grazing phase. The second factor was grass height, High Height (AA) and Low Height (BA), 25 and 10 cm (intended heights), respectively. As a third factor, the days of collection were evaluated after the application of N, which were performed at 2°, 4°, 6°, 8°, 10°, 12° and 14° day after the application of urea. For the grain culture, another factor (2x2x7x4) was added, with increasing doses of N: 0; 50; 100 and 150 kg ha-1, and 0; 100; 200 and 300 kg ha-1, for the bean and corn crop, respectively. They were allocated in subplots within each plot, at the time of application of the N in cover in the treatment N-Fertilization Grains. The evaluation of ammonia volatilization was performed by the method of static semi-open collectors and the quantification of the ammonia content was performed by the colorimetry method. Ammonia volatilization losses for both winter and summer crops were influenced by the treatments in which they were submitted and were highly dependent on the climatic conditions at the time of N application. The accumulated losses caused by ammonia volatilization by nitrogen fertilization (urea) were minimal, being lower than 1.5% in the two years of evaluation in the grazing phase. In the bean and corn cultivation phase the maximum accumulated ammonia volatilization loss observed was 5.37% and 4.0%, respectively. Higher grazing pressure resulted in lower losses due to ammonia volatilization during the grazing phase and, conversely, during the grazing phase a higher grazing pressure applied to previously cultivated grazing resulted in higher losses due to volatilization of ammonia.

CAPES / A intensificação da produção em sistemas integrados de produção, basifica-se na sustentabilidade do mesmo, buscando os melhores arranjos para sustentação de bons resultados. A adubação é de extrema importância para o sucesso na produtividade, sendo a nitrogenada que requer maior atenção na produção, principalmente, de gramíneas. No cultivo de pastagens muitas vezes há um negligenciamento na adubação, sendo maior quando se trata para cobertura. Com base nesta premissa, o trabalho tem o objetivo de encontrar uma resposta para a adubação nitrogenada aplicada na aveia branca, bem como se esta adubação é mais responsiva em doses únicas ou parceladas, em sistema de cortes e para cobertura vegetal. O experimento foi desenvolvido na UTFPR-DV, em delineamento fatorial 2 x 6 (manejo x níveis de nitrogênio), blocos ao acaso, com três repetições e parcelas subdivididas. As parcelas receberam quatro doses de nitrogênio 0, 60, 120 e 180 kg ha-1 de N associados a três formas de parcelamento do fertilizante (aplicação em dose única bem como o parcelamento das doses de 120 e 180 kg ha-1 de N em duas e três aplicações de 60 kg N ha-1 respectivamente). A adubação nitrogenada foi realizada a lanço, sendo a ureia (45% N) a fonte de nitrogênio utilizada. As avaliações realizadas na aveia foram determinação de taxa de acúmulo, matéria seca, taxa de recuperação e eficiência de uso do nitrogênio e teor de proteína bruta. Os dados obtidos foram submetidos à análise de variância e quando verificado significância pelo teste F as médias foram comparadas pelo Teste Tukey a 5% de probabilidade de erro. A taxa de acumulo média variou de 39,36 a 59,42 kg ha-1 de MS para sem cortes e de 41,73 a 62,67 kg ha-1 de MS com cortes. A produção de matéria seca para sem cortes o acumulado variou de 6240 a 10266,67 kg ha-1 de MS nos níveis estudados, com cortes, foi de 4865 a 7593,33 kg ha-1 de MS. A máxima eficiência técnica foi obtida com 149 kg ha-1 de N. A eficiência do uso do nitrogênio decresceu com o aumento dos níveis de nitrogênio. Em geral, a taxa de recuperação também decresceu com o aumento dos níveis de nitrogênio. A proteína bruta variou para as parcelas sem cortes de 12,1 a 16,06% e com cortes de 13,41 a 16,92%. Conclui-se que houve imobilização de nitrogênio aplicado nas maiores doses, sendo mais expressivo nos tratamentos que não receberam cortes. A partir de 120 kg ha-1 de N o parcelamento pode ser interessante quando não se pode ter perda temporal pela imobilização. / The intensification of production in integrated production systems, is based on the sustainability of the same, seeking the best arrangements to sustain good results. Fertilization is of extreme importance for the success in productivity, being nitrogenous that requires more attention in the production, mainly of grasses. In cultivation of pastures there is often negligence in fertilization, being greater when it comes to coverage. Based on this premise, the objective of this work is to find an answer for the nitrogen fertilization applied in white oats, as well as if this fertilization is more responsive in single or split doses, in a system of cuts and for vegetal cover. The experiment was developed in UTFPR-DV, in a 2 x 6 factorial design (management x nitrogen levels), randomized blocks, with three replicates and subdivided plots. The plots received four nitrogen doses 0, 60, 120 and 180 kg ha-1 of N associated to three forms of fertilizer application (single dose application as well as the splitting of doses of 120 and 180 kg ha-1 of N in two and three applications of 60 kg N ha-1 respectively). Nitrogen fertilization was carried out in the haul, with urea (45% N) being the source of nitrogen used. The evaluations carried out in the oats were determination of accumulation rate, dry matter, recovery rate and efficiency of nitrogen use and crude protein content. The data were submitted to analysis of variance and when verified by means of the F test, the means were compared by the Tukey test at 5% error probability. The mean accumulation rate ranged from 39.36 to 59.42 kg ha-1 of DM for uncut and 41.73 to 62.67 kg ha-1 of DM with cuts. The dry matter yield for uncrowded accumulated varied from 6240 to 10266.67 kg ha-1 of DM at the studied levels, with cuts, from 4865 to 7593.33 kg ha-1 of MS. The maximum technical efficiency was obtained with 149 kg ha-1 of N. The efficiency of the use of nitrogen decreased with the increase of the nitrogen levels. In general, the recovery rate also decreased with increasing nitrogen levels. The crude protein varied for the plots without cuts of 12.1 to 16.06% and with cuts of 13.41 to 16.92%. It was concluded that there was immobilization of nitrogen applied at higher doses, being more expressive in treatments that did not receive cuts. From 120 kg ha-1 of N, the splitting can be interesting when there is no temporal loss due to immobilization.

CAPES / A intensificação da produção em sistemas integrados de produção, basifica-se na sustentabilidade do mesmo, buscando os melhores arranjos para sustentação de bons resultados. A adubação é de extrema importância para o sucesso na produtividade, sendo a nitrogenada que requer maior atenção na produção, principalmente, de gramíneas. No cultivo de pastagens muitas vezes há um negligenciamento na adubação, sendo maior quando se trata para cobertura. Com base nesta premissa, o trabalho tem o objetivo de encontrar uma resposta para a adubação nitrogenada aplicada na aveia branca, bem como se esta adubação é mais responsiva em doses únicas ou parceladas, em sistema de cortes e para cobertura vegetal. O experimento foi desenvolvido na UTFPR-DV, em delineamento fatorial 2 x 6 (manejo x níveis de nitrogênio), blocos ao acaso, com três repetições e parcelas subdivididas. As parcelas receberam quatro doses de nitrogênio 0, 60, 120 e 180 kg ha-1 de N associados a três formas de parcelamento do fertilizante (aplicação em dose única bem como o parcelamento das doses de 120 e 180 kg ha-1 de N em duas e três aplicações de 60 kg N ha-1 respectivamente). A adubação nitrogenada foi realizada a lanço, sendo a ureia (45% N) a fonte de nitrogênio utilizada. As avaliações realizadas na aveia foram determinação de taxa de acúmulo, matéria seca, taxa de recuperação e eficiência de uso do nitrogênio e teor de proteína bruta. Os dados obtidos foram submetidos à análise de variância e quando verificado significância pelo teste F as médias foram comparadas pelo Teste Tukey a 5% de probabilidade de erro. A taxa de acumulo média variou de 39,36 a 59,42 kg ha-1 de MS para sem cortes e de 41,73 a 62,67 kg ha-1 de MS com cortes. A produção de matéria seca para sem cortes o acumulado variou de 6240 a 10266,67 kg ha-1 de MS nos níveis estudados, com cortes, foi de 4865 a 7593,33 kg ha-1 de MS. A máxima eficiência técnica foi obtida com 149 kg ha-1 de N. A eficiência do uso do nitrogênio decresceu com o aumento dos níveis de nitrogênio. Em geral, a taxa de recuperação também decresceu com o aumento dos níveis de nitrogênio. A proteína bruta variou para as parcelas sem cortes de 12,1 a 16,06% e com cortes de 13,41 a 16,92%. Conclui-se que houve imobilização de nitrogênio aplicado nas maiores doses, sendo mais expressivo nos tratamentos que não receberam cortes. A partir de 120 kg ha-1 de N o parcelamento pode ser interessante quando não se pode ter perda temporal pela imobilização. / The intensification of production in integrated production systems, is based on the sustainability of the same, seeking the best arrangements to sustain good results. Fertilization is of extreme importance for the success in productivity, being nitrogenous that requires more attention in the production, mainly of grasses. In cultivation of pastures there is often negligence in fertilization, being greater when it comes to coverage. Based on this premise, the objective of this work is to find an answer for the nitrogen fertilization applied in white oats, as well as if this fertilization is more responsive in single or split doses, in a system of cuts and for vegetal cover. The experiment was developed in UTFPR-DV, in a 2 x 6 factorial design (management x nitrogen levels), randomized blocks, with three replicates and subdivided plots. The plots received four nitrogen doses 0, 60, 120 and 180 kg ha-1 of N associated to three forms of fertilizer application (single dose application as well as the splitting of doses of 120 and 180 kg ha-1 of N in two and three applications of 60 kg N ha-1 respectively). Nitrogen fertilization was carried out in the haul, with urea (45% N) being the source of nitrogen used. The evaluations carried out in the oats were determination of accumulation rate, dry matter, recovery rate and efficiency of nitrogen use and crude protein content. The data were submitted to analysis of variance and when verified by means of the F test, the means were compared by the Tukey test at 5% error probability. The mean accumulation rate ranged from 39.36 to 59.42 kg ha-1 of DM for uncut and 41.73 to 62.67 kg ha-1 of DM with cuts. The dry matter yield for uncrowded accumulated varied from 6240 to 10266.67 kg ha-1 of DM at the studied levels, with cuts, from 4865 to 7593.33 kg ha-1 of MS. The maximum technical efficiency was obtained with 149 kg ha-1 of N. The efficiency of the use of nitrogen decreased with the increase of the nitrogen levels. In general, the recovery rate also decreased with increasing nitrogen levels. The crude protein varied for the plots without cuts of 12.1 to 16.06% and with cuts of 13.41 to 16.92%. It was concluded that there was immobilization of nitrogen applied at higher doses, being more expressive in treatments that did not receive cuts. From 120 kg ha-1 of N, the splitting can be interesting when there is no temporal loss due to immobilization.

Orientador: Rogério Peres Soratto / Coorientador: Adalton Mazetti Fernandes / Banca: Dirceu Maximino Fernandes / Banca: José Magno Queiroz Luz / Resumo: O nitrogênio (N) é um dos nutrientes extraídos em maior quantidade pela batateira e tem grande impacto no desempenho dessa cultura. A resposta da cultura da batata à adubação nitrogenada é dependente de diversos fatores, o que torna essencial o manejo correto do N, maximizando assim a absorção deste pela planta. Além disso, a aplicação de doses insuficientes ou demasiadamente elevadas de N pode reduzir a produtividade e a qualidade dos tubérculos produzidos e representar prejuízos aos produtores e riscos ao ambiente. Neste sentido, a estimativa da necessidade de N, mediante leituras do índice relativo de clorofila (IRC) nas folhas da cultura, com o clorofilômetro portátil, pode ser uma alternativa viável para tornar o manejo do N mais preciso. Contudo, ainda existe a necessidade de estabelecimento de critérios para a utilização dessa ferramenta na cultura da batata. Dessa forma, os objetivos deste trabalho foram: a) avaliar a correlação entre o IRC, obtido mediante leituras do clorofilômetro portátil, e o teor de N da folha de duas cultivares de batata (Agata e Electra), em diversos estádios de desenvolvimento e b) avaliar qual valor (90% e 95%) do índice de suficiência de N (ISN), calculado com base nas medidas IRC nas folhas em relação ao tratamento referência, é o mais adequado para indicar o momento da adubação nitrogenada em duas cultivares de batata e, consequentemente, proporcionar maior produtividade, qualidade de tubérculos e eficiência de utilização do N aplicado. D... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract:Nitrogen (N) is one of the nutrients extracted in greater quantity by potato and has a great impact on the performance of this crop. The response of the potato crop to the nitrogen fertilization is dependent on several factors, which makes essential the correct management of N, thus maximizing its absorption by the plant. In addition, the application of insufficient or excessively high doses of N may reduce the productivity and quality of the tubers produced and represent damages to the producers and risks to the environment Therefore, the estimation of the need for N, through readings of the relative index of chlorophyll (IRC) in the leaves of the culture, with the portable chlorophyllometer, can be a viable alternative to make N management more accurate. However, there is still a need to establish criteria for the use of this tool in the potato crop. Thus, the objectives of this study were: a) evaluate the correlation between the IRC, obtained by readings of chlorophyll, and the N concentration in leaves of two potato cultivars (Agata e Electra) in various stages of development, and b) evaluate what value (90% or 95%) of N sufficiency index (NSI), calculated based on RCI measures in the leaves regarding the treatment reference, is best suited to indicate the time of N fertilizer in two cultivars potato and hence to higher tuber yields and quality, and N-use efficiency. In the year 2016, during winter season four experiments were carried out in the field conditions, two at Lageado Experimentl Farm (Site 1) and two in a private potato farm (Site 2), both in the municipality of Botucatu. In each site were carried out one experiment with each cultivar. The design used in each experiment will be randomized blocks, with six N managements (M1: 80 kg ha-1 N in the planting furrow + 80 kg ha-1 at 10 days after emergence (DAE) + 80 kg ha-1 at 30 DAE + 80 kg ha-1 at 45 DAE (reference); ... / Mestre

Orientador: Carlos Alexandre Costa Crusciol / Coorientador: Nilza Patricia Ramos / Banca: Cristinano Alberto de Andrade / Banca: Raffaela Rossetto / Resumo: A operação de recolhimento da palha de cana-de-açúcar trouxe a oportunidade ímpar de agregar sustentabilidade e renda extra ao setor sucroalcooleiro. Com isto, dúvidas surgiram sobre os efeitos que esta prática ocasionaria ao sistema solo-planta, e quais seriam as necessidades de alteração nas práticas de manejo, principalmente quando se trata da adubação nitrogenada, além de permitir a exploração de tecnologia pouco explorada, como a interação entre planta e microrganismos fixadores de nitrogênio. Neste sentido, o objetivo desta pesquisa foi avaliar a dinâmica de decomposição de quantidades variáveis de palha pela aplicação de adubo nitrogenado mineral ou inoculação com bactérias diazotróficas. Para isto acompanhou-se a decomposição da palha durante a primeira soca da variedade IACSP 95-5000, testando três níveis de recolhimento (36, 64 e 100%), o equivalente à 4.300; 7.400; e 11.500 kg ha-1 de palha mantida em campo e duas técnicas de cobertura: 120 kg ha-1 de nitrato de amônio e a inoculação foliar com a mistura de cinco estirpes bacterianas (Azospirillum amazonense, Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae, Herbaspirillum rubrisubalbicans e Burkholderia tropica). O experimento foi instalado em fatorial 3x2, distribuídos em blocos ao acaso com parcela subdivida no tempo (coletas). Para avaliar a decomposição foi utilizado o método de "litterbags", com coletas regulares aos 0, 101, 180, 235, 285 e 319 dias após a instalação em campo, permitindo o acompan... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The sugarcane straw recovering process brought an unique opportunity to join sustainability and income to sugarcane sector.Thus, doubts arose about the outcome that this practice would have on soil-plant system, and beyond, what would be necessary to change in management system, especially when it comes to nitrogen fertilization, both for amount and source selected, as well as poorly exploited technology using, such the relationship between plant and nitrogen-fixing microorganisms.Therefore, the research aimed to evaluate sucargacane straw levels and its effect on decomposition process by using mineral fertilizer and NBF inoculant. The experiment proceeded by following straw decomposition of IACSP 95-5000 first ratoon, testing three recovering rates (36,64 e 100%), wich represents 4,300; 7,400; and 11,500 kg ha-1 of straw left in the field and two top dressing techniques: 120 kg ha- 1 of ammonium nitrate and leaf inoculation with five bacterial strains (Azospirillum amazonense, Gluconacetobacter diazotrophicus, Herbaspirillum seropedicae, Herbaspirillum rubrisubalbicans and Burkholderia tropica). The experiment was installed in 3x2 factorial arranged in randomized blocks with design scheme of split plot (sampling). The decomposition process was accompanied by litterbags method with sampling at 0, 101, 180, 235, 285 and 319 days after installation wich allowed to determine rate (%) and dry mass of biomass, carbon, structural carbohydrates, lignin, and nitrogen (kg ha-1 ) besides C: N ratio. The C N contents (%) collected from 0-5cm layer was evaluated before harvesting, as well as 0-10 cm, but the last one were sampled from row and crop interrow. The results were submitted to variance analysis with regression and when significant differences were detected, means were compared by Tukey (p <0.05). At the end of the experiment, carbon and straw dry mass constant and decomposition rate ... / Mestre

Kikuyu pasture was fertilized at low and high levels of nitrogen (N), namely 50 and 200 kg N/ha, after mowing and clearing the plots, to induce low and high levels of N in the herbage. The subsequent growth was harvested at 20-, 30- and 40-d re-growth. These treatments were conducted in spring, summer and autumn. Treatments included level of N, stage of re-growth and season as variables in digestion trials using sheep and voluntary feed intake (VFI) trials using long yearling heifers in pens equipped with Calan gates. Nitrogen fertilization level had no impact on herbage dry matter digestibility (DMD). Stage of re-growth influenced digestibility in the spring and summer, the highest values recorded in the 30-d treatment. However, in the autumn, the 20-d re-growth recorded the greatest digestibility. Digestibility declined as the season progressed. Digestibility was not correlated to any of the chemical fractions measured in the herbage, including in vitro DM digestibility (IVDMD). Voluntary feed intake (VFI) followed a similar trend to digestibility, with peak values recorded for the 30-d treatment in the spring and summer, while the 20-d material induced the greatest intake in the autumn. Nitrogen fertilization had a negative impact on VFI over all seasons. Similarly to digestibility, VFI was not correlated to any of the chemical fractions measured, but was correlated to digestibility and moisture concentration of the herbage. Nitrogen degradability was determined using the in situ bag technique. Differences (p<0.05) were recorded for the quickly degradable N (a) and potentially degradable N (b) fractions within season, but not for the degradation rate of the slowly degraded fraction (c) per hour. The effective degradability (dg) was not influenced by N fertilization level in the spring, while N fertilization increased the dg values in the summer and autumn. Stage of re-growth exerted a positive effect (P<0.05) on the dg values. Rumen pH, rumen ammonia and blood urea nitrogen (BUN) levels were measured in rumen fistulated sheep. Rumen pH increased also with increasing level of N fertilization and declined with advancing stage of herbage re-growth in the autumn. Rumen ammonia increased with time of sampling post feeding to 4 hrs and then tended to decline by 6 hrs. Nitrogen fertilization level influenced rumen ammonia levels (p<0.05), with the low N level producing the lowest rumen ammonia levels. Rumen ammonia levels were highest at 20-d re-growth stage in summer and at the 40-d re-growth stage in autumn. DM concentration of the herbage had an inverse relationship with rumen ammonia. BUN levels were increased by high N fertilization and were positively correlated to rumen ammonia levels. Five years of digestibility data (82 digestion trials) and three years of intake trials (38 trials) data was pooled. These data, chemical composition of the herbage and the daily maximum temperatures, rainfall and evaporation recorded at and prior to the digestion and intake trials at Cedara were analysed using multiple regression techniques. Rainfall and temperature in the period of cutting and fertilization had a negative effect on digestibility, irrespective of the stage of re-growth at harvesting, 20, 30 or 40 days later, and a combination of the two proved significant, accounting for the most variance in DDM. Temperature depressed DMD by 11.4 g/kg DM per degree rise in temperature (Degrees C). Temperatures recorded during the cutting and fertilization phase were highly negatively correlated to VFI, irrespective of stage of re-growth. The DM concentration of the herbage as fed accounting for 32% of the variance in DMD, the NPN content of the herbage accounting for only 12.2% of the variance and the ash concentration of the herbage accounting for 15.9% of the variance in digestibility. Non-protein nitrogen was negatively correlated to VFI. Both DMD and VFI were highly negatively influenced by the moisture concentration of the herbage. Overall, the results of these trials demonstrated that environmental factors such as rainfall and temperature had a far greater impact on the digestibility of kikuyu herbage than the chemical composition, which had a minimal effect. Nitrogen fertilization did not influence herbage digestibility overall, but exerted a highly negative impact on voluntary intake. / Thesis (Ph.D.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.